My Master Signature Key is used only for signing keys and collecting signatures. If you wish to sign my key, please use this one. Please verify the fingerprint with me in person before signing it, of course.

Because my Daily Use Key is signed with my Master Signature Key, it is not necessary or useful for anyone else to sign it directly. Just import both of the keys, update your trustdb, and all should be well.

In the past, I kept a Backup Key, in addition to the Daily Use Key, but with the same properties. It was used for encrypting backups that I store in the cloud. I no longer see the point of doing that; I'll just encrypt backup with my Daily Use Key. That key identifies me, and only I may decrypt my backups.